Vehicular brake rotors

ABSTRACT

Vehicular brake rotor formed by powder metallurgy including metals such as titanium powder.

FIELD OF THE INVENTION

This invention relates to manufacturing vehicular parts by powdermetallurgy techniques and more particularly to making vehicular brakerotors by powder metallurgy using powders, such as titanium powder.

BACKGROUND OF THE INVENTION

Traditionally automotive brake rotors have been made using cast ironwhich provides good wear resistance and high temperature properties.However, cast iron is dense relative to other materials so that a castiron brake rotor is heavy. A heavy brake rotor is undesirable for atleast three reasons. First, a heavy brake rotor contributes to theoverall weight of a motor vehicle and thus reduces its fuel efficiencyand increases its emissions. Secondly, a brake rotor is part of theunsprung vehicle weight, meaning the weight below the springs. Unsprungweight adds to the noise, vibration, and harshness (sometimes referredto as “NVH”) associated with vehicle operation. When unsprung weight isreduced, NVH is usually improved. Thirdly, a brake rotor is a vehiclepart that requires rotation during use. Accordingly a heavier brakerotor requires additional energy to increase and decrease rotationalspeed. Reducing weight of a vehicle rotor also lowers vibration duringrotation. Carbon-carbon composites, ceramics, and cermets have also beenconsidered for use in brake rotors but they are expensive and have notachieved widespread adoption as vehicle rotors.

Titanium has been considered as a brake rotor material in Murphy U.S.Pat. No. 5,521,015 and Martino U.S. Pat. No. 5,901,818, incorporatedherein by reference. Titanium has excellent strength to weightproperties, and it retains strength at high temperatures. However, highcosts have heretofore prevented widespread adoption of titanium and itsalloys in vehicle brake rotors. Accordingly there still remains a greatneed for a low cost process for manufacturing titanium brake rotors.

Other brake rotors are shown in U.S. Pat. No. 4,278,153, which disclosesa brake disk frictional module composed of sintered metallic materialreinforced throughout its entire volume by a grid system of pure metalor metallic alloy. The friction module may be manufactured by sinteringthe metallic material with the grid reinforcement in either a mold orwithin the brake disk cup. The internal reinforcement of the frictionalmodule prevents spalling weight loss, friction coefficient decay, orother physical defect as caused by frictional strain during use. Thereinforcement material reduces the overall temperature of the diskduring use, and aids frictional coefficient of the disk because of themetallic compatibility of the metallic material and grid system.

U.S. Pat. No. 5,620,791 discloses metal and ceramic matrix compositebrake rotors comprising an interconnected matrix embedding at least onefiller material. In the case of metal matrix composite materials, atleast one filler material comprises at least about 26% by volume of thebrake rotor for most applications, and at least about 20% by volume forapplications involving passenger cars and trucks. In a preferredembodiment of the present invention, the metal matrix composite brakerotor comprises an interconnected metal matrix containing at least about28% by volume of a particulate filler material and more preferably atleast about 30% by volume. Moreover, the composite rotors of the presentinvention exhibit a maximum operating temperature of at least about 900°F. and preferably at least about 950° F. and even more preferably atleast about 975° F. and higher.

U.S. Pat. No. 4,381,942 discloses a process for the production oftitanium-based alloy members by powder metallurgy. This process consistsof: (a) preparing a titanium or titanium alloy powder having a grainsize distribution between 100 and 1000 μm, (b) depositing on said powdera coating of a material such that on contact with the titanium ortitanium alloy it forms a liquid phase at a temperature T.sub.1 which isbelow the allotropic transformation temperature T of the titanium ortitanium alloy constituting the said powder, (c) introducing the thuscoated powder into a mould, and (d) hot compressing this powder in themould at a pressure of 10 to 30 MPa at a temperature between T₁ and Tfor a time such that a complete densification of the powder is obtained.This invention has application to the construction of discs for turbineswith integrated blades.

U.S. Pat. No. 4,719,074 discloses a metal-ceramic composite articleproduced by fitting a projection formed on a ceramic member into a holeformed in a metallic member having a hardened region and an unhardenedregion on its surface such that the ceramic member is monolithicallybonded to the metallic member and the deformed region of the metallicmember resulting from the fitting is located within its unhardenedrange, has a high bonding force between the ceramic member and themetallic member and is adapted to be used in engine parts, such asturbocharger rotor, gas turbine rotor and the like, and other structuralparts exposed to high temperature or to repeating loads, by utilizingthe heat resistance, wear resistance and high strength of the ceramic.

U.S. Pat. No. 5,053,192 discloses deforming combustion products byextrusion at an extrusion temperature chosen in the range from 0.3 T₁ toT₂, wherein T₁ is the melting point of a hard phase of the combustionproducts and T₂ is the melting point of a binder material in a container(5) made up of vertically extending segments (12) defining spaces (13)with one another and having a die (14) and a heat insulated sizingmember (17) the temperature conditions of extrusion being controlled bymeans of a unit (21) having a temperature pick-up (22) and a member (23)receiving information from the pick-up (22) and sending a command formoving the punch (10).

U.S. Pat. No. 5,139,720 discloses manufacturing a sintered ceramicmaterial using the heat generated in a thermit reaction as a heatingsource, a pre-heating is applied preceding to the sintering step or amixture comprising: (A) at least one ceramic powder, (B) at least onenon-metallic powder selected from the group consisting of carbon, boronand silicon, and (C) a metal powder and/or a non-metallic powder otherthan the above-mentioned (B) is used. Homogeneous and dense sinteredceramic material or sintered composite ceramic material can be obtainedby this method, and the fine texture thereof, and the phaseconstitution, the phase distribution and the like of the compositeceramic phase can be controlled sufficiently.

U.S. Pat. No. 5,701,943 discloses a metal matrix composite made byblending non-metal reinforcement powder with powder of metal or metalalloy matrix material, heating to a temperature high enough to causemelting of the matrix metal/alloy and subjecting the mixture to highpressure in a die press before solidification occurs.

A principal advantage of the present invention is that it enables, forexample, titanium brake rotors to be manufactured at a relatively lowcost. The invention also provides, for example, titanium brake rotors atsubstantially lower cost than prior art carbon-carbon composite brakerotors. Other advantages of the invention will become readily apparentto persons skilled in the art from the following specification andclaims.

SUMMARY OF THE INVENTION

The process of the invention includes steps of mixing particles oftitanium or a titanium alloy with a nonmetallic material to form amixture, compressing the mixture to form a preform, and sintering thepreform at an elevated temperature to form a vehicle component such as abrake rotor. Titanium powder may contain some impurities, principallyabout 0.12 wt % titanium dioxide. The titanium powder has a medianparticle size of about 1-100 microns, preferably about 3-30 microns andmore preferably about 5-10 microns. Particle surface area is greaterthan about 25 m²/g preferably about 50-250 m²/g. Aspect ratio is about 5to 300. Suitable titanium alloys include, for example, Ti-6Al-4V,Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-10V-2Fe-3Al, and Ti-5Al-2.5Sn.

The mixture contains about 30-95 parts by weight titanium or titaniumalloy and about 5-70 parts by weight of the nonmetallic material.Preferably the mixture contains about 60-80 parts by weight titanium ortitanium alloy and about 20-40 parts by weight nonmetallic material. Thenonmetallic material can be provided as particles, fibers, whiskers,flakes, or mixtures thereof. Suitable nonmetallic materials are ceramicsincluding silicon carbide, boron carbide, tungsten carbide, chromiumcarbide, alumina, zirconium oxide, silicon nitride, boron nitride, andtitanium diboride, solely or in various combinations with each other.Optionally the mixture may contain up to about 10 parts by weight of anorganic binder, as explained below in more detail. The ingredients arepreferably mixed together by milling, such as jet milling. Aparticularly preferred mixture contains about 70 parts by weighttitanium powder and about 30 parts by weight silicon carbide powder.Optionally, up to about 10 parts by weight boron nitride may also beincluded.

Optional ingredients in the mixture include up to about 10 parts byweight of an organic binder and up to about 20 parts by weight boronnitride. The organic binder improves green strength before thetitanium-containing mixture is sintered. Sintering converts the organicbinder to metal carbides, water, and carbon dioxide. Selection of anappropriate binder requires that any organic content remaining in theproduct not affect performance, even at MOT (maximum operatingtemperature).

The predominant failure mode of metal brake rotors is by surfacescuffing. As a brake rotor is subjected to progressively more severeconditions, the temperature of the rotor continues to rise until itreaches a temperature at which a glaze is formed on the rubbingsurfaces. The temperature at which the rotor surface breaks down andscuffing ensues is the Maximum Operating Temperature or MOT. Rotorbreakdown is followed by rapid wear of the brake pads and a rise intemperature as measured by the pad thermocouples. The MOT for brakerotors is measured by dynamometer tests in accordance with SAE J212entitled “Brake System Dynamometer Test Procedures—Passenger Car”published by SAE International, of Warrendale, Pa., in January, 1998.

It is an object of the invention to provide an improved brake rotor.

In addition, there is provided a process for making an improved titaniumbrake rotor. The process comprises providing titanium or titanium alloypowder having, for example, an average particle size of about 1-100microns, a mean aspect ration of about 5 to 300, and specific surfacearea of at least about 25 m²/g. Further, the process includes mixing atitanium or titanium alloy powder with a nonmetallic material to providea mixture. A brake rotor mold is provided and a first layer of themixture is poured into the mold. Then, a second layer comprisingtitanium powder is poured into the mold on top of the first layer. Athird layer of the mixture is then poured on top of the titanium powderlayer. The powder in the mold is compressed to form a preformed brakerotor or green body, and the preform is sintered to provide a brakerotor having first and second opposed sides having nonmetalliccontaining wear layers on each of the sides.

Preferably, the mixture contains 5-40 wt. % nonmetallic powder. Thenonmetallic powder is comprised of at least one of the group consistingof silicon carbide, boron carbide, tungsten carbide, chromium carbide,alumina, zirconium oxide, silicon nitride, boron nitride, and titaniumdiboride, solely or in various combinations with each other.

The preferred nonmetallic powder is silicon carbide. The sintering stepcan be carried out in a temperature range of 1400° to 2200° F.,preferably in the range of 1500° to 2100° F. The sintering step may becarried out utilizing microwaves or conventionalradiation-conduction-convection heating. In the microwave process, theheat is generated internally within the material instead of originatingfrom external heating sources, which results in rapid heating andshorter heating cycles with less energy requirements as compared toconventional heating methods. Microwaves are electromagnetic radiationwith wavelengths ranging from 1 mm to 1 m in free space and frequencybetween 0.3 GHz to 300 GHz. Typical frequencies for materials processingare 0.915 GHz, 2.45 GHz, 5.8 GHz, and 24.124 GHz with 2.45 GHz as thestandard for industrial and scientific applications. The rotor isdensified to at least 50-75% after sintering, preferably to 95-100%.

A coating to provide a second wear surface may be applied by plasmaspraying the surfaces of the wear layers. Thus, the rotor can include acoating applied to the first and second sides of the rotor. The coatingcan include a bond coat containing nickel, an intermediate coatcomprising zirconium oxide, chromium carbide, and nickel, and a top coatcomprising zirconium oxide and chromium carbide. The top coat cancomprise about 65 to 75 parts by weight zirconia and about 25 to 35parts by weight chromium carbide, and the bond coat further can containaluminum. The top coat and the intermediate coat can contain a lesseramount of nickel and aluminum than the bond coat.

Specifically, to first and second sides of the rotor, there may beapplied a coating comprised of a bond coat of about 4.5 wt % aluminumand about 95.5 wt % nickel; an intermediate coat of about 70 parts byweight zirconia, 30 parts by weight of a composition as used for thebond coat, and 10 parts by weight chromium carbide; and a top coat ofabout 70 parts by weight zirconium oxide and about 30 parts by weightchromium carbide.

The inventive process for making a brake rotor further comprisesproviding metallic powder having, for example, an average particle sizeof about 1-20 microns, a mean aspect ratio of about 5 to 300, andspecific surface area of at least about 25 m²/g. The process includesmixing the metallic powder with about 5 to 70 wt. % of a nonmetallicmaterial to provide a mixture. A brake rotor mold is provided, and afirst layer of the mixture is poured into the mold. A second layer ofthe metallic powder is then poured into the mold on top of the firstlayer. A third layer of the mixture is poured on top of the titaniumpowder layer. The powder in the mold is compressed to form a preformedbrake rotor, and the preform is sintered to provide a brake rotor havingfirst and second sides having nonmetallic containing wear layers on eachof the sides.

The metallic powder is selected from the group consisting of titanium,steel, stainless steel, cast iron, and alloys thereof.

Further, the invention includes a process for making an improvedtitanium brake rotor. The process comprises providing titanium or atitanium alloy powder having, for example, an average particle size ofabout 1-20 microns, a mean aspect ratio of about 5 to 300, and specificsurface area of at least about 25 m²/g. Further, the process includesmixing a titanium or titanium alloy powder with 5 to 60 wt. % of asilicon carbide powder or material to provide a mixture. A brake rotormold is provided, and a first layer of the mixture is poured into themold. Then, a second layer of the titanium powder is poured into themold adjacent the first layer. A third layer of the mixture is thenpoured on top of the titanium powder layer. The powder in the mold iscompressed to form a preformed brake rotor, and the preform is sinteredto provide a brake rotor having first and second opposed sides havingsilicon carbide containing wear layers on each of the sides.

Thus, an improved titanium brake rotor is provided comprised of acentral layer of a metal or metal alloy sandwiched between two outsidelayers comprised of a mixture of metal or metal alloy and a nonmetallicmaterial, which outside layer provides brake wear layers on the rotor.These rotors may be formed as described herein. That is, the titaniumbrake rotor may be comprised of a central layer of a titanium ortitanium alloy or other such metal, e.g., iron, steel, or stainlesssteel and alloys thereof, sandwiched between two outside layerscomprised of a mixture of titanium or titanium alloy and silicon carbideto provide brake wear layers on the rotor. The rotor can be formed byprocesses described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a brake rotor according to the presentinvention.

FIG. 2 shows an elevational view of the brake rotor illustrated in FIG.1.

FIG. 3 is a cross-section, taken along III-III of FIG. 1, whichschematically illustrates different layers associated with a brake rotoraccording to the present invention.

FIG. 4 illustrates a typical brake assembly employing a brake rotoraccording to the present invention.

FIG. 5 is a cross section of a brake rotor of the invention.

FIG. 6 is a cross-section of a mold for making preforms of brake rotorsof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with a preferred embodiment of the present inventionillustrated in FIG. 1, a brake rotor 1 includes two opposite brakingsurfaces 3, one of which is shown in FIG. 1. The braking surfaces areoriented parallel to one another.

The rotor 1 has an outer peripheral surface 11 and an inner peripheralsurface 13. The rotor can have a series of holes 5 distributed on itsbraking surfaces and passing through the rotor, from one braking surface3 on one side of the rotor, to the braking surface 3 on the other sideof the rotor. A plurality of lugs 7 are arranged uniformly about theinner peripheral surface 13 of the rotor 1 and extend radially inwardly.Each lug 7 is appropriately provided with a hole 9 for connection with ahub member.

FIG. 2 is an elevational view of the brake rotor illustrated in FIG. 1.The outer peripheral surface 11 (see FIG. 1) of the rotor 1 is indentedabout substantially its entire circumference with a groove 17.

FIG. 3 provides a detailed and exaggerated cross-sectional view of rotor1, the view being taken along line III-III of FIG. 1. As illustratedschematically in FIG. 3, rotor comprised of a substrate 2, which carriesa braking surface 3 on each of its two broad sides. In the illustratedembodiment, each braking surface 3 is composed of two layers, which arereferred to herein as “coats”. Thus, each braking surface is composed ofa bond coat 19 and a top coat 21. The particular composition of theselayers will be discussed more fully below, as well as methods forapplying the same to the braking surfaces 3. Generally, however, bondcoat 19 may include a thin layer comprised of nickel. The top coat 21 isa ceramic composition of zirconium oxide and chromium carbide,preferably in the range of 65 to 75 parts by weight zirconium oxide and25 to 35 parts by weight chromium carbide. Preferably, bond coat 19 andtop coat 21 are preferably applied to the braking surfaces 3 by plasmaspraying techniques which are well known to those of ordinary skill inthe art. Following application of the materials by plasma spraying, thebraking surface is ground smooth. As used herein with respect to thebond coat 19 and the top coat 21, the term “nickel” includes nickel,nickel alloys such as nickel-chromium alloys, and nickel aluminide.

As a general rule, increasing the chromium carbide relative to thezirconium oxide increases the wear resistance of the braking surface,while increasing the zirconium oxide relative to the chromium carbideincreases the coefficient of friction of the braking surface.

Coatings composed of more than two layers may, of course, be used, andmay even be preferred, for instance for the purpose of makingtransitions between different coefficients of thermal expansion lessabrupt, or for the purpose of introducing various kinds of materialsoffering special advantages. The Example below, for instance, uses threelayers, a bond coat, an intermediate coat, and a top coat.

FIG. 4 illustrates a typical brake assembly in which a brake rotoraccording to the present invention is employed. Various components ofthe brake assembly are indicated by name. It will be understood that the“brake shoes” may be considered as including friction pads. Unlike thesingle-plane rotor of FIGS. 1 to 3, the rotor of FIG. 4 is a vaned rotorcomposed of two planes, each having an outwardly facing braking surfacecomposed of coats, as described with reference to FIG. 3. The two planesare separated by inwardly situated vanes. The rotors of the inventionmay, or may not, have holes 5 in the braking surfaces, and, toillustrate this variation, the vaned rotor illustrated in FIG. 4 doesnot have holes 5. Vaned rotors may be manufactured using jigs to holdthe vanes in place relative to the planes, followed by TIG welding ofthe vanes to the interior surfaces of the planes. Alternatively, vanedrotors may cast as one unit, using casting processes, such as investmentcasting, or may be formed by powder metallurgy techniques describedherein. Wear layers may be formed on the vaned rotor by the powdermetallurgy technique described herein.

Suitable materials for substrate 2 are cast iron, steel, titanium andits alloys as described above, and titanium composites made by powdermetallurgy techniques. Sintered titanium composites made by powdermetallurgy techniques are particularly preferred.

In accordance with my invention about 20 parts by weight titaniumdiboride powder were mixed with about 80 parts by weight titanium powderhaving less than 1 wt % impurities. The principal impurity in thetitanium powder was titanium oxide, comprising about 0.12 wt % of thepowder. The titanium powder was supplied by International TitaniumPowder, LLC, of Lockport, Ill. Processes for making the titanium powderare described in Armstrong et al. U.S. Pat. Nos. 5,779,761; 5,958,106;and 6,409,797. The Armstrong et al. patents are assigned toInternational Titanium Powder and their disclosures are incorporatedherein by reference to the extent consistent with the present invention.The titanium powder has an aspect ratio of about 15 and specific surfacearea of about 100 m²/g. Its median particle size is about 5-10 micronsalthough the particles tend to clump together into larger agglomerates.The titanium and titanium diboride powders were blended with about 1 wt% of an organic binder, isostatically pressed at room temperature intothe shape of a brake rotor, sintered at an elevated temperature, andcooled overnight to ambient temperature.

The brake rotor described above may be used without any coating for someapplications. For most uses however, a coating is applied to the brakingsurfaces 3. In preparation for receipt of the coating the brakingsurface 3 is grit-blasted or sand-blasted in a cabinet capturing theused media. Suitable sandblasting techniques are well known in the art.

The braking surfaces 3 are preferably coated with nickel aluminide to acoating thickness of about 0.005 inch. Thickness of the bond coating 19ranges from about 0.001 inch to about 0.03 inch. The alloy is preferablyapplied by plasma spraying. Next, an intermediate coat 20 is applied byplasma spraying. The intermediate coat comprises about 70 parts byweight yttria stabilized zirconium oxide, 30 parts by weight of thecomposition used for the bond coat, and about 10 parts by weightchromium carbide.

Finally a top coat 21 is applied also by plasma spraying. The top coatcomprises about 70 parts by weight yttria stabilized zirconium oxide andabout 30 parts by weight chromium carbide.

Referring now to FIG. 5, there is illustrated another embodiment of theinvention. FIG. 5 shows an improved rotor 50 formed using metal powdersand metallurgical sintering techniques. That is, rotor 50 has a centralcore 52 sandwiched between two wear surfaces or layers 54 and 56. Core52 is fabricated from metal powders, such as titanium, steel, stainlesssteel, and cast iron, and may contain controlled levels of nonmetallicmaterial to aid in heat transfer or dissipation. The nonmetallicmaterial may be selected from silicon carbide, boron carbide, tungstencarbide, chromium carbide, alumina., zirconium oxide, silicon nitride,boron nitride, and titanium diboride, solely or in various combinationswith each other.

In accordance with the present invention, central core 52 is combinedwith two outside wear layers 54 and 56. Wear layers 54 and 56 may becomprised of the same metal as central core 52 or a different metalcompatible with the central core. However, as presently understood, itis preferred that the wear layers utilize the same metal as the core.

Wear layers 54 and 56 are comprised of a metal powder and a nonmetallicmaterial or powder. The metal powder is comprised of at least one metalfrom the group consisting of titanium, steel, and stainless steel, asnoted. Typical alloys for the titanium are Ti-6Al-4V, Ti-6Al-6V-2Sn,Ti-6Al-2Sn-4Zr-2Mo, Ti-10V-2Fe-3Al, and Ti-5Al-2.5Sn.

The nonmetallic material or powder selected for the wear layer is atleast one of the group selected from silicon carbide, boron carbide,tungsten carbide, chromium carbide, alumina., zirconium oxide, siliconnitride, boron nitride, and titanium diboride, solely or in variouscombinations with each other.

Metal powder such as titanium powder useful in the invention preferablyhas a particle size in the range of about 1-20 μm, a mean weight ratioof about 5-300 and a surface area in the range of 5 to 150 m²/g.,typically about 25 m²/g.

Typically, the mixture of metallic, e.g., titanium, and nonmetallic,e.g., silicon carbide, particles comprises 5-60 wt. nonmetallicmaterial, although in some instances the range for nonmetallic materialmay extend beyond this range. For purposes of sintering, this step maybe carried out in a temperature range of 1400° to 2200° F., typically1500° to 2100° F. As an example, heat may be supplied using microwavesgenerated in a 2.45 GHz multimode microwave furnace, which consists of afurnace chamber with vacuum capability, a microwave mode stirrer thatbreaks up any standing waves and creates a multimode field within thefurnace chamber, and a 6 kW microwave generator that provides microwavesto the chamber via waveguides.

In the present invention, densification is at least 50% and usually morethan 75%. However, the process is capable of providing rotors having90-100% densification.

In certain instances where performance braking is required, e.g., racecars, it may be desirable to apply a plasma coating, as describedearlier, to the outside surface 58 of layers 54 and 56.

Referring now to FIG. 6, there is illustrated a mold 60 in cross sectionand press 62 for applying pressure to powdered materials in mold 60 forpurposes of producing a green body. Mold 60 shows a recess 64 containingpowders for forming into a rotor. Press 62 has a complementaryprotrusion 66 for applying pressure to the powder in the mold. In oneembodiment of the invention, a first layer of powder 68 is provided inthe mold. This first layer of powder comprises, for example, titaniumpowder mixed with silicon carbide powder in the desired proportions tosubsequently provide the wear layers. The second layer 70 of powdercomprises a metallic powder, such as titanium powder, which is spreaduniformly over the first layer 68. A third layer 72, e.g., titaniumpowder mixed with silicon carbide powder, is spread over second layer70, as shown in FIG. 6. Thereafter, press 62 is used to press the powderin the mold to provide a green body. Pressures up to 1500 tons can beused. Thereafter, the green body is sintered to provide a rotor. Therotor can be machined after sintering to provide the final dimensions.

All ranges provided herein include all the numbers within the range, asif specifically set forth.

Having described the presently preferred embodiments, it is to beunderstood that the invention may be otherwise embodied within the scopeof the appended claims.

1. A process for making an improved titanium brake rotor, comprising:(a) providing titanium or a titanium alloy powder having an averageparticle size of about 1-20 microns, a mean aspect ratio of about 5 to300, and specific surface area of at least about 25 m²/g; (b) mixingwith said titanium or titanium alloy powder, nonmetallic material toprovide a mixture; (c) providing a brake rotor mold: (i) pouring a firstlayer of said mixture into said mold; (ii) pouring a second layer ofsaid titanium powder into said mold on top of said first layer; and(iii) pouring a third layer of said mixture on top of said nonmetallicpowder layer; (d) compressing the powder in said mold to form apreformed brake rotor; and (e) sintering said preform to provide a brakerotor having first and second opposed sides having nonmetalliccontaining wear layers on each of said sides.
 2. The process inaccordance with claim 1 including providing 5-60 wt. % nonmetallicmaterial in said mixture.
 3. The process in accordance with claim 1wherein said nonmetallic material is at least one of the groupconsisting of silicon carbide, boron carbide, tungsten carbide, chromiumcarbide, alumina., zirconium oxide, silicon nitride, boron nitride, andtitanium diboride, solely or in various combinations with each other. 4.The process in accordance with claim 1 wherein said nonmetallic materialis silicon carbide.
 5. The process in accordance with claim 1 whereinsaid sintering is performed in a temperature range of 1400° to 2200° F.6. The process in accordance with claim 1 wherein said sintering isperformed in a temperature range of 1500° to 2100° F.
 7. The process inaccordance with claim 1 wherein sintering is carried out by utilizingmicrowaves or conventional radiation-conduction-convection heating. 8.The process in accordance with claim 1 wherein said brake rotor isdensified to 50-75%.
 9. The process in accordance with claim 1 whereindensification is at least 95%.
 10. The process in accordance with claim1 wherein densification is in the range of 96-100%.
 11. The process ofclaim 1 including applying a coating to said first and second sides ofsaid rotor, said coating comprising a bond coat containing nickel, anintermediate coat comprising zirconium oxide, chromium carbide, andnickel, and a top coat comprising zirconium oxide and chromium carbide.12. The process of claim 11 wherein said top coat comprises about 65 to75 parts by weight zirconia and about 25 to 35 parts by weight chromiumcarbide.
 13. The process of claim 11, the bond coat further containsaluminum.
 14. The process of claim 13, wherein the top coat and theintermediate coat contain a lesser amount of nickel and aluminum thanthe bond coat.
 15. The process of claim 1 including applying to firstand second sides, coatings comprised of a bond coat of about 4.5 wt %aluminum and about 95.5 wt % nickel; an intermediate coat of about 70parts by weight zirconia, 30 parts by weight of a composition as usedfor the bond coat, and 10 parts by weight chromium carbide; and a topcoat of about 70 parts by weight zirconium oxide and about 30 parts byweight chromium carbide.
 16. The process of claim 1 wherein said rotoris a single or double vaned rotor.
 17. A process for making a brakerotor, comprising: (a) providing metallic powder having an averageparticle size of about 1-20 microns, a mean aspect ratio of about 5 to300, and specific surface area of at least about 25 m²/g; (b) mixingwith said metallic powder, 5-70 wt. % of a nonmetallic material toprovide a mixture; (c) providing a brake rotor mold: (i) pouring a firstlayer of said mixture into said mold; (ii) pouring a second layer ofsaid metallic powder into said mold on top of said first layer; and(iii) pouring a third layer of said mixture on top of said metallicpowder layer; (d) compressing the powder to form a preformed brakerotor; and (e) sintering said preform to provide a brake rotor havingfirst and second sides having nonmetallic containing wear layers on eachof said sides.
 18. The process in accordance with claim 17 wherein themetallic powder is selected from the group consisting of titanium,steel, stainless steel, and cast iron.
 19. The process in accordancewith claim 17 wherein the nonmetallic material is selected from thegroup consisting of silicon carbide, boron carbide, tungsten carbide,chromium carbide, alumina., zirconium oxide, silicon nitride, boronnitride, and titanium diboride, solely or in various combinations witheach other.
 20. The process in accordance with claim 17 includingproviding 5-60 wt. % nonmetallic material in said mixture.
 21. Theprocess in accordance with claim 17 wherein said nonmetallic material issilicon carbide.
 22. The process in accordance with claim 17 whereinsaid sintering is performed in a temperature range of 1400° to 2200° F.23. The process in accordance with claim 17 wherein said sintering isperformed in a temperature range of 1500° to 2100° F.
 24. The process inaccordance with claim 17 wherein sintering is carried out by utilizingmicrowaves.
 25. The process in accordance with claim 17 wherein saidbrake rotor is densified to 50-75%.
 26. The process in accordance withclaim 17 wherein densification is at least 95%.
 27. The process inaccordance with claim 17 wherein densification is in the range of96-100%.
 28. A process for making an improved titanium brake rotor,comprising: (a) providing titanium or a titanium alloy powder having anaverage particle size of about 1-20 microns, a mean aspect ratio ofabout 5 to 300, and specific surface area of at least about 25 m²/g; (b)mixing with said titanium or titanium alloy powder, 5 to 60 wt. % of asilicon carbide material to provide a mixture; (c) providing a brakerotor mold: (i) pouring a first layer of said mixture into said mold;(ii) pouring a second layer of said titanium powder into said moldadjacent said first layer; and (iii) pouring a third layer of saidmixture into said mold adjacent said titanium powder layer; (d)compressing the powder to form a preformed brake rotor; and (e)sintering said preform to provide a brake rotor having first and secondopposed sides having silicon carbide wear layers on each of said sides.29. An improved titanium brake rotor comprised of a central layer of ametal or metal alloy sandwiched between two outside layers comprised ofa mixture of metal or metal alloy and a nonmetallic material providingwear layers on said rotor.
 30. The brake rotor in accordance with claim29 wherein the metal or metal alloy is titanium or titanium alloy. 31.The brake rotor in accordance with claim 29 wherein the nonmetallicmaterial is silicon carbide.
 32. The brake rotor in accordance withclaim 29 wherein the metal or metal alloy is titanium, steel orstainless steel or alloys thereof.
 33. The brake rotor in accordancewith claim 29 wherein the central layer contains nonmetallic material.34. The brake rotor in accordance with claim 29 wherein the rotor isformed from powder material.
 35. The brake rotor in accordance withclaim 34 wherein said rotor is sintered at 1400° to 2200° F.
 36. Thebrake rotor in accordance with claim 34 wherein said rotor is sinteredat 1500° to 2100° F.
 37. The brake rotor in accordance with claim 34wherein said rotor was sintered using microwaves.
 38. The brake rotor inaccordance with claim 34 wherein said rotor has a density of at least95%.
 39. The brake rotor in accordance with claim 34 wherein said rotorhas a density between 96 and 100%.
 40. An improved titanium brake rotorcomprised of a central layer of a titanium or titanium alloy sandwichedbetween two outside layers comprised of a mixture of titanium ortitanium alloy and silicon carbide to provide wear layers on said rotor.41. The titanium brake rotor in accordance with claim 40 wherein saidcentral layer is a double vane.
 42. An improved titanium brake rotorcomprised of a central layer of titanium or titanium alloy sandwichedbetween two outside layers comprised of a mixture of titanium andsilicon carbide, thereby providing wear layers on said rotor.
 43. Thetitanium brake rotor in accordance with claim 42 wherein said centrallayer is a double vane.
 44. The rotor of claim 40 having a bond coatcontaining nickel, an intermediate coat comprising zirconium oxide,chromium carbide, and nickel, and a top coat comprising zirconium oxideand chromium carbide applied to each side.
 45. The rotor of claim 40wherein said top coat comprises about 65 to 75 parts by weight zirconiaand about 25 to 35 parts by weight chromium carbide.
 46. The rotor ofclaim 40, the bond coat further containing aluminum.
 47. The rotor ofclaim 40, wherein the top coat and the intermediate coat contain alesser amount of nickel and aluminum than the bond coat.
 48. The rotorof claim 40 including applying to first and second sides, coatingscomprised of a bond coat of about 4.5 wt % aluminum and about 95.5 wt %nickel; an intermediate coat of about 70 parts by weight zirconia, 30parts by weight of a composition as used for the bond coat, and 10 partsby weight chromium carbide; and a top coat of about 70 parts by weightzirconium oxide and about 30 parts by weight chromium carbide.
 49. Aprocess for making a brake rotor component comprising: (a) mixing about30-95 parts by weight titanium or a titanium alloy with about 5-70 partsby weight of a nonmetallic particulate material, the titanium ortitanium alloy comprising a powder having an average particle size ofabout 1-20 microns, a mean aspect ratio of about 5 to 300, and specificsurface area of at least about 25 m²/g; (b) compressing the mixture toform a preform, (c) sintering the preform at an elevated temperature toform a brake rotor.
 50. The process of claim 49 wherein step (b)includes adding an organic binder to the mixture.
 51. The process ofclaim 49 wherein said particulate material comprises a ceramic selectedfrom the group consisting of silicon carbide, boron carbide, tungstencarbide, chromium carbide, alumina, silicon nitride, boron nitride,titanium diboride, and mixtures thereof.
 52. The process of claim 49wherein said particulate material has a thermal conductivity at leasttwice that of titanium.
 53. The process of claim 49 wherein saidparticulate material has a higher melting point than titanium.
 54. Theprocess of claim 49 wherein said rotor has an outer surface, and furthercomprising: (d) coating said outer surface with a bond coat containingnickel, an intermediate coat comprising zirconium oxide, chromiumcarbide, and nickel, and a top coat comprising about 65 to 75 parts byweight zirconium oxide and about 25 to 35 parts by weight chromiumcarbide.
 55. The process of claim 54 wherein said step of coatingcomprises plasma spraying.
 56. The process of claim 54, the bond coatfurther containing aluminum.
 57. The process of claim 56, wherein thetop coat and the intermediate coat contain a lesser amount of nickel andaluminum than the bond coat.
 58. The process of claim 54 wherein saidouter surface comprises a bond coat of about 4.5 wt % aluminum and about95.5 wt % nickel; an intermediate coat of about 70 parts by weightzirconia, 30 parts by weight of a composition as used for the bond coat,and 10 parts by weight chromium carbide; and a top coat of about 70parts by weight zirconium oxide and about 30 parts by weight chromiumcarbide.
 59. The process of claim 54 wherein the zirconium oxide isyttria stabilized.
 60. A brake rotor made by the process of claim 54,said outer surface comprising a braking surface.